Theophylact of Ohrid

When he says, "it is no longer I who do it," he removes the blame from the body. Who then does evil? Sin, which, according to John Chrysostom, is a vicious and sin-loving will. And this will is not a creation of God, but our own movement. The will in itself is a creation of God; but the will directed toward a particular end is something of our own, an act of our free choice. It was said above what sin is, that is, the tyranny of sin, which carries away our mind through pleasure.

Commentary on Romans ↗

Clement of Alexandria

Even if the heretics who are opposed to the Creator suppose that in the next sentence Paul was speaking against him when he says, "I know that in me, that is in my flesh, there dwells no good thing," yet let them read what precedes and follows this. …

The Stromata Book 3 ↗

Thomas Aquinas

Then, when he says, now if I do that which I will not, he concludes to what he had previously proposed, saying, now if I do that which I will not, it is no more I that do it, but sin that dwells in me. This, too, has been explained earlier. But it should be noted that in virtue of the same middle term, i.e., which I will not, the Apostle concludes to the two things he had proposed above, namely, the goodness of the law, when he said, now if I do that which I will not, I consent to the law, that it is good, and the dominion of sin in …

Commentary on Romans ↗